Ventricular catheter ablation has been established as the most desirable from cost and patient safety point of view approach in treating cardiac arrhythmias, yet its success rate has not broad acceptance. This is primarily because this treatment modality relies almost entirely on the experience and abilities of the physician in charge to identify the ablative site through endocardial mapping. In this grant application we aim to investigate the ability of a new method to rapidly, reliably and safely identify the site of origin of the arrhythmia. Our method relies on assigning properties of an equivalent moving dipole to each phase of the cardiac cycle and then inversely resolving the properties (location and strength) of the dipole. Our hypothesis is that the inverse dipole solution will accurately locate the arrhythmogenic focus at the point in the cardiac cycle when electrical activity is still focal, as the depolarization wave emerges from the focus. We will build a state-of-art system aimed to provide the cardiac electrophysiologist with a tool that will facilitate the identification of the site of the arrhythmia in the heart and will enable the accurate guiding of the ablation catheter to the site of origin of that arrhythmia. We will evaluate its performance by means of saline tank and animal studies. In the latter study, we will ultimately compare the location of the site identified by means of the equivalent dipole solution with the site initially identified by the operator as well as the site which ultimately results in the abolition of inducibility of ventricular tachycardia. The ability to perform three dimensional mapping and view the arrhythmia in real-time represents a step ahead from the standard fluoroscopic two-dimensional imaging or activation mapping. Furthermore our methodology promises to reduce the time required to perform the mapping and make it well tolerated from the patient. The impact of successful catheter ablation of ventricular tachycardia may be to (i) reduce the incidence of sudden cardiac death, (ii) reduce the frequency of implantable cardioverter shocks, and (iii) decrease the need of anti-arrhythmic medications with their potentially pro-arrhythmic and/or other side effects. PUBLIC HEALTH RELEVANCE: Ventricular catheter ablation has been established as the most desirable from cost and patient safety point of view approach in treating cardiac arrhythmias, yet its success rate has not broad acceptance. This is primarily because this treatment modality relies almost entirely on the experience and abilities of the physician in charge to identify the ablative site through endocardial mapping. This proposal investigates the ability of a new method to rapidly, reliably and safely identify the site of origin of the arrhythmia and help guide the ablation catheter to that site.